PROJECT SUMMARY Bronchopulmonary dysplasia (BPD) remains the most common chronic lung disease of infancy, affecting 40% of infants born extremely preterm (EPT, born at <28 completed weeks gestation). Severe BPD is characterized by chronic supplemental oxygen exposure, mechanical ventilation dependence, and prolonged and recurrent hospitalizations within the first year of life. Despite advances in neonatal intensive care unit (NICU) management, the incidence of BPD remains unacceptably high. Our research seeks to identify novel, reliable and mechanistic-based biomarkers that can help guide management of our critically ill EPT patients, and inform the development of new approaches to BPD prevention. A well-supported scientific premise is that environmental exposures that induce lung injury through oxidative stress (OS) play a central role in BPD pathophysiology. Putative early life exposures include uteroplacental insufficiency during pregnancy, and hyperoxia in the early postnatal period. Reactive oxygen and nitrogen species are central to BPD pathophysiology as they directly damage DNA and proteins necessary for lung growth and repair. These electrophiles enter the blood from absorption in the lungs from oxidation of lipids and other molecules. Once in the blood, electrophiles react with available proteins to form addition products, or adducts. When bound to human serum albumin (HSA), these adducts become more stable (28 days in circulation) than the scavenged reactive electrophiles. The HSA-Cys34 residue is an important ?nucleophilic hotspot? for OS-related adducts, accounting for 80% of plasma antioxidant capacity. Unbiased, untargeted adductomics pipelines for HSA-Cys34 have recently been developed, which have led to discovery of long-lived exposure biomarkers of chronic disease arising from OS. Application of untargeted adductomics in an EPT infant population would provide new opportunities to investigate the neonatal exposome as it relates to BPD. In the proposed study, we will utilize the resources of a large well-established NICU birth cohort coupled with the unique resources of the Northwestern Adductomics Lab. Our central hypothesis is that OS-related adducts can identify meaningful perinatal and neonatal exposures that predict BPD. In Aim 1, will identify HSA-Cys34 adducts and intrauterine exposure pathways of BPD through untargeted and targeted adductomics of archived cord blood plasma from 100 EPT births (N=50 BPD cases and 50 non-BPD controls), and 50 term control births. We will quantify abundant and discordant adducts, stratified by infant gender, gestational age, placental histologic lesions of uteroplacental insufficiency, and with other perinatal covariates. In Aim 2, we will perform targeted adductomics in postnatal blood to test the hypothesis that HSA-Cys34 adducts that correlate with postnatal cumulative oxygen exposure are predictive of BPD. We will prospectively enroll 50 EPT infants at two Level III+ NICUs of the Prentice Birth Cohort, and collect postnatal blood at 1 month, 2 months, and 36 weeks corrected age (primary endpoint for BPD diagnosis).